Wednesday 15 April 2009 19.01 EDT
First published on Wednesday 15 April 2009 19.01 EDT

Senior civil servants exaggerated the damage done by Home Office leaks that provoked the arrest of Conservative frontbencher Damian Green, the Commons home affairs select committee will say today.

The report by the all-party committee of MPs also criticises the police operation, which was headed by Bob Quick, the Metropolitan police assistant commissioner who resigned from the force last week after causing a security lapse that led to a counterterrorism operation having to be brought forward.

The police handling of the arrest "owed more to the Keystone Kops than Softly Softly", Keith Vaz, the chairman of the committee, said last night.

Green, a shadow immigration minister, and Christopher Galley, a Home Office official, are still waiting to find out whether they will be charged in relation to the investigation, which provoked fierce controversy at Westminster last year because the decision to arrest Green and raid his office in the Commons was seen by many MPs as an assault on parliamentary privilege. Green strongly denies wrongdoing and Galley has issued a statement saying he acted in the public interest.

"Although we understand that the police were anxious to operate discreetly, some of their efforts may actually have complicated the situation. Twenty-four police officers, and a number of strategy groups, including some of the most senior police officers, were involved in the investigation, strategy, arrest of Mr Green and searching of his office," Vaz said.

In their report, the MPs identified more than 20 conversations that took place on the day of the arrest between police officers and the Home Office, Cameron's office and the mayor of London, who were all being kept informed. As a result "all decisions made - who was informed, when, and of precisely what - [have been] subject to question and interpretation as interested parties probe to see whether anyone could have influenced or hindered the police operation," the MPs said.

To avoid this happening again, the committee recommended "the adoption by the police of a protocol setting out the exceptional circumstances in which a politician would be informed of any police operation while it is under way".

The police were asked to investigate after an internal Home Office inquiry into more than 20 leaks in 2007 and 2008 failed to make any progress. Sir David Normington, the permanent secretary at the Home Office, consulted the Cabinet Office, where officials were worried about other government leaks, and the Cabinet Office formally invited the police to intervene.

The Cabinet Office letter to the police said: "We are in no doubt that there has been considerable damage to national security already as a result of some of these leaks and we are concerned that the potential for future damage is significant."

However, the committee concluded that there was a "clear mismatch" between the impression given by the letter and the evidence given by Normington, who told the MPs that most of the Home Office leaks had not raised issues of national security.

It added that the Cabinet Office should revise its rules to make it clear that the police should only get involved in leak inquiries if there is suspicion that a criminal offence has occurred.